In　this　work,　Si-doped　cross　linked　carbon　nanofibers　(Si/CNF)　were　prepared　by　electrospinning　polyacrylonitrile　(PAN)　solutions　containing　polyhedral　oligomeric　silsesquioxane　(POSS)　as　Si　source,　followed　by　thermal　treatments.　Scanning　electron　microscope　(SEM)　observations　showed　the　smooth　surfaces　of　pure　PAN　nanofibers,　while　PAN/POSS　nanofibers　with　obviously　rough　or　porous　surfaces　were　obtained　with　relatively　high　POSS　content.　X-ray　diffraction　(XRD)　identified　the　presence　of　POSS　in　the　composite　nanofibers.　After　thermal　treatments,　cross　linked　Si/CNFs　with　various　morphologies　were　obtained.　Energy-dispersive　X-ray　(EDX)　and　X-ray　photoelectron　spectroscopy　(XPS)　analyses　confirmed　the　successful　incorporation　of　Si　into　CNFs.　Raman　spectra　suggested　the　degree　of　carbon　ordering　of　Si/CNFs　reduced　slightly　when　compared　with　pure　CNF.　The　obtained　nanofibers　exhibited　typical　performances　of　electric　double-layer　capacitors　(EDLC).　The　specific　capacitance　of　Si/CNF　showed　a　moderate　increase　with　POSS　content　and　reached　a　maximum　of　175　F/g　at　1　A/g　with　PAN:　POSS　equal　to　100:5.　Meanwhile　Si/CNFs　exhibited　excellent　cycling　stability　after　1000　cycles.　The　influence　of　POSS　on　the　capacitive　performance　might　be　attributed　to　the　combined　effects　of　evolution　of　morphology,　conductivity　and　surface　properties　of　Si/CNFs.